In light of energy prices and environmental concerns, alternative processes for the production of energy such as electricity and its thermal equivalent are needed. In that vein many processes have been used to convert waste heat to electricity. A process limited to geothermal fluid sources is described in, for example, U.S. Pat. No. 5,660,042 which employs using the waste heat from a naturally occurring hot water source to make electricity. Another process is described in U.S. Pat. No. 6,571,548 in which heat is extracted from the exhaust of a gas turbine unit to drive a generator that generates electricity.
Yet another potential process was described in World Oil Vol. 228 No. 9 (September 2007) where an attempt was made to generate electricity from the waste water of an oil field using a unit that was “field-proven in other situations, but never used in an oil field.” It was believed that this would work “Because both of these water streams [were] of high quality” with “the only contaminant [approaching] the surface discharge limit is chlorine.” Therefore, it was surmised that the water “should not present a fouling problem in the geothermal unit's heat exchangers as the water temperature decreases.” Similar attempts to use geothermal heat are discussed at PROCEEDINGS. Thirty-Second Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, Calif., Jan. 22-24, 2007 SGP-TR-183 and Oil and Gas Journal, McKenna et al., Sep. 5, 2005. pp. 34-40. Thus, up until the present invention problems such as fouling of process equipment prevented using heat from oil and/or gas operation for useful energy.
Thus, while many processes have been invented to generate electricity from a conventional geothermal source like hot water or steam, no process exists to extract heat directly from a produced, single or multiphase hydrocarbon, fluid and convert it to a useful energy source such as electricity. Accordingly, new processes are needed which can effectively and efficiently convert heat contained in produced fluids to a useful energy source like electricity.
The instant invention provides new processes and apparatuses for use in effectively and efficiently converting heat contained in produced fluids like oil, gas, water and mixtures thereof to a beneficial use such as producing electricity or other useful energy such as heating another stream or fluid.
In one embodiment, the instant invention relates to a process for generating a heated working fluid that may be capable of converting energy. The process comprises gathering a heat containing fluid comprising one or more hydrocarbons from an oil or gas operation wherein said heat-containing fluid comprises at least a substantially vapor phase and a substantially liquid phase. If multiphase, the substantially vapor phase is then preferably separated from said substantially liquid phase. Next, a vapor heat exchanger and a liquid heat exchanger may then be employed to exchange at least a portion of the heat contained in each of said phases to a working fluid thereby producing a heated working fluid. The heated working fluid may be capable of converting energy.
In another embodiment the invention relates to a process for generating a heated working fluid that may be capable of converting energy. The process comprises first gathering a heat containing fluid comprising one or more hydrocarbons from an oil or gas operation. Next, the heat containing fluid is passed to one or more heat exchangers to exchange at least a portion of the heat contained in said heat containing fluid to a working fluid. This produces a heated working fluid that may be capable of converting energy. Preferably, the heat containing fluid is a mixture comprising oil, water, and one or more gases. The working fluid may be water which includes, for example, untreated or treated water, softened water, as well as, deoxygenated process water and may be employed in, for example, a closed loop intermediate system.
In another embodiment, the instant invention relates to an apparatus for generating a heated working fluid that may be capable of converting energy. The apparatus comprises a wellhead that is capable of producing a heat containing fluid comprising one or more hydrocarbons wherein said heat-containing fluid comprises at least a substantially vapor phase and a substantially liquid phase. The apparatus also comprises a separator that is operably connected to the wellhead. The separator is capable of separating said substantially vapor phase from said substantially liquid phase. A vapor heat exchanger is operably connected to the separator to accept the substantially vapor phase from the separator and exchange at least a portion of the heat contained in said substantially vapor phase to a working fluid thereby producing a heated working fluid capable of converting energy. A liquid heat exchanger is operably connected to the separator to accept the substantially liquid phase from the separator and exchange at least a portion of the heat contained in said substantially liquid phase to a working fluid thereby producing a heated working fluid capable of converting energy. The apparatus also typically comprises one or more pipes, e.g. one or more conductors, operably connected to the vapor heat exchanger, the liquid heat exchanger, or both to transfer the heated working fluid to, for example, a power plant to generate electricity from said heated working fluid or as thermal energy to, for example, heat another stream in need of heating.